Hi marksru16, I don't know about the Cannondale Synapse, but the Giant Defy Advanced is a good choice. I opted for the LOOK looking for getting something different (already own a Giant TCR-C1) and less common in the road. I suggest you try them all if you can, in my case I didn't road test neither; went to see the Defy in my LBS but didn't actually saw the LOOK in person before buying (but read quite a lot about it).

Regards,

Francisco